New report: Catastrophic Queensland floods linked to global warming

Researchers have now linked Queensland's 2010 catastrophic floods with global warming. And they warn that the double hazard of long-term ocean warming and rising atmospheric temperatures makes the risk of extreme rainfall greater in years to come. Tim Radford reports for Climate News Network.

Warming oceans helped to worsen Australia’s floods five years ago by intensifying rainfall

IN 2010, during a natural cyclic Pacific phenomenon called La Niña, sea surface temperatures in the Indian Ocean and the western Pacific were high, and the air became saturated with moisture.

When the clouds billowed over Queensland, they deposited so much water that 35 people died, 28,000 homes were flooded and 100,000 people were left without electricity. Lake Eyre, a normally dry lakebed in the country’s interior, filled with water.

La Niña is the supposedly cooler little sister of the notorious El Niño, associated with warmer than usual waters in the eastern equatorial Pacific. Researchers have already warned that it could play a role in future floods: Dr Ummenhofer and her colleagues have looked back in time to find that it has already done so.

Climatologists are normally reluctant to ascribe any one weather event to climate change driven by rising carbon dioxide levels as a consequence of the human combustion of fossil fuels: that is because climate is what people expect, but weather is what happens.

But this is the first direct link with any one episode of flooding. One prediction of the Woods Hole team’s modelling experiments is that because of warmer sea surface temperatures, Australia is now three times more likely to experience unprecedented rainfall during a strong La Niña event.

Matthew England, of the Australian Research Council’s Centre of Excellence for Climate System Science, and a co-author wrote:

The additional warming of the oceans has profound impacts on the atmosphere. It increases the amount of moisture in the atmosphere and can intensify rain-producing circulation conditions.

This is why in 2010/11 more moisture was brought onshore along Australia’s east coast. Stronger rising motion over the northeast resulted in higher rainfall, making it more likely for Australia to suffer extreme rainfall conditions during this strong La Niña.

Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.